Aldose reductase inhibition by 5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]me]-1H-indene-3-acetic acid

ABSTRACT

Disclosed are new methods of using 5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-acetic acid or a therapeutically acceptable salt thereof with an organic or inorganic base for the treatment of complications associated with diabetes mellitus. The compound inhibits lens aldose reductase in a diabetic mammal.

This application is a continuation-in-part of application Ser. No.160,873, filed June 19, 1980 now U.S. Pat. No. 4,307,114, issued Dec.22, 1981, and expressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to new methods of using5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid or a therapeutically acceptable salt thereof with an organic orinorganic base for the treatment of complications associated withdiabetes mellitus.

For many years diabetes mellitus has been treated with two establishedtypes of drugs, namely insulin and oral hypoglycemic agents. These drugshave benefited hundreds of thousands of diabetics by improving theirwell-being and prolonging their lives. However, the resulting longevityof diabetic patients has led to complications such as neuropathy,nephropathy, retinopathy and cataracts. These complications have beenlinked to the undesirable accumulation of sorbitol in diabetic tissue,which in turn result from the high levels of glucose characteristic ofthe diabetic patient.

In mammals, including humans, the key enzyme involved in the conversionof hexoses to polyols (the sorbitol pathway) is aldose reductase. J. H.Kinoshita and collaborators, see J. H. Kinoshita et al., Biochem.Biophys. Acta, 158, 472 (1968) and references cited therein, havedemonstrated that aldose reductase plays a central role in the etiologyof galactosemic cataracts by effecting the conversion of galactose todulcitol (galactitol) and that an agent capable of inhibiting aldosereductase can prevent the detrimental accumulation of dulcitol in thelens. Furthermore, a relationship between elevated levels of glucose andan undesirable accumulation of sorbitol has been demonstrated in thelens, peripheral nervous cord and kidney of diabetic animals, see A.Pirie and R. van Heyningen, Exp. Eye Res., 3, 124 (1964); L. T. Chylackand J. H. Kinoshita, Invest. Ophthal., 8, 401 (1969) and J. D. Ward andR. W. R. Baker, Diabetol., 6, 531 (1970).

5-Fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid and its preparation are described by T.-Y. Shen et al., U.S. Pat.No. 3,654,349, issued Apr. 4, 1972 and D. F. Hinkley and J. B. Conn,U.S. Pat. No. 3,647,858, issued Mar. 7, 1972.5-Fluoro-2-methyl-1-[[4-(methylthio)phenyl]-methylene]-1H-indene-3-aceticacid has anti-inflammatory, anti-pyretic and analgesic activity, D. E.Duggan et al., Biochem. Pharm., 27, 2311 (1978).

Surprisingly,5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]-methylene]-1H-indene-3-aceticacid or its therapeutically acceptable salt thereof with an organic orinorganic base, now has been found to be a potent inhibitor of lensaldose reductase. This new found property renders5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid, or a salt thereof, useful for the treatment of diabeticcomplications.

SUMMARY OF THE INVENTION

According to the present invention, a method is provided for preventingor relieving a diabetes mellitus associated condition in a diabeticmammal by administering to the mammal an alleviating or prophylaticamount of5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid or a therapeutically acceptable salt thereof with an organic orinorganic base. The latter compound is especially useful for preventingor relieving a diabetes mellitus associated complication consisting ofcataracts, neuropathy, nephropathy and retinopathy in a diabetic mammal.

DETAILED DESCRIPTION OF THE INVENTION

5-Fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid forms salts with suitable therapeutically acceptable inorganic andorganic bases. These derived salts possess the same activity as theparent acid and are included within the scope of this invention. Theacid is transformed in excellent yield into the correspondingtherapeutically acceptable salt by neutralization of said acid with theappropriate inorganic or organic base. The salts are administered in thesame manner as the parent acid compound. Suitable inorganic bases toform these salts include, for example, the hydroxides, carbonates,bicarbonates or alkoxides of the therapeutically acceptable alkalimetals or alkaline earth metals, for example, sodium, potassium,magnesium, calcium and the like. Suitable organic bases include thefollowing amines; benzylamine; lower mono-, di- and trialkylamines, thealkyl radicals of which contain up to three carbon atoms, such asmethylamine, dimethylamine, trimethylamine, ethylamine, di- andtriethylamine, methylethylamine, and the like; mono-, di- andtrialkanolamines, the alkanol radicals of which contain up to threecarbon atoms, for example, mono-, di- and triethanolamine;alkylene-diamines which contain up to six carbon atoms, such ashexamethylenediamine; cyclic saturated or unsaturated bases containingup to six carbon atoms, such as pyrrolidine, piperidine, morpholine,piperazine and their N-alkyl and N-hydroxylakyl derivatives, such asN-methyl-morpholine and N-(2-hydroxyethyl)-piperidine, as well aspyridine. Furthermore, there may be mentioned the correspondingquaternary salts, such as the tetraalkyl (for example tetramethyl),alkyl-alkanol (for example methyltriethanol and trimethyl-monoethanol)and cyclic ammonium salts, for example the N-methylpyridinium,N-methyl-N-(2-hydroxyethyl)-morpholinium N,N-dimethylmorpholinium,N-methyl-N-(2-hydroxyethyl)-morpholinium, N,N-dimethylpiperidiniumsalts, which are characterized by having good water-solubility. Inprinciple, however, there can be used all the ammonium salts which arephysiologically compatible.

The transformations to the salts can be carried out by a variety ofmethods known in the art. For example, in the case of the inorganicsalts, it is preferred to dissolve5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid in water containing at least one equivalent amount of a hydroxide,carbonate, or bicarbonate corresponding to the inorganic salt desired.Advantageously, the reaction is performed in a water-miscible, inertorganic solvent, for example, methanol, ethanol, dioxane, and the likein the presence of water. For example, such use of sodium hydroxide,sodium carbonate or sodium bicarbonate gives a solution of the sodiumsalt. Evaporation of the solution or addition of a water-misciblesolvent of a more moderate polarity, for example, a lower alkanol, forinstance, butanol, or a lower alkanone, for instance, ethyl methylketone, gives the solid inorganic salt if that form is desired.

To produce an amine salt,5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid is dissolved in a suitable solvent of either moderate or lowerpolarity, for example, ethanol, methanol, ethyl acetate, diethyl etherand benzene. At least an equivalent amount of the amine corresponding tothe desired cation is then added to that solution. If the resulting saltdoes not precipitate, it can usually be obtained in solid form byaddition of a miscible diluent of lower polarity, for example, benzeneor petroleum ether, or by evaporation. If the amine is relativelyvolatile, any excess can easily be removed by evaporation. It ispreferred to use substantially equivalent amounts of the less volatileamines.

Salts wherein the cation is quaternary ammonium are produced by mixing5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid with an equivalent amount of the corresponding quaternary ammoniumhydroxide in water solution, followed by evaporation of the water.

5-Fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid or an addition salt thereof with pharmaceutically acceptableorganic or inorganic bases may be administered to mammals, for example,man, cattle or rabbits, either alone or in dosage forms, i.e., capsulesor tablets, combined with pharmacologically acceptable excipients, seebelow. Advantageously5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid can be given orally. However, the method of administering5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid is not to be construed as limited to a particular mode ofadministration. For example,5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid can be administered topically directly to the eye in the form ofdrops of sterile, buffered ophthalmic solutions, preferably of pH7.2-7.6. Topical administration is especially useful for treatingcataracts and retinopathy in a diabetic mammal. Also, it can beadministered orally alone or in solid form containing such excipients asstarch, milk sugar, certain types of clay and so forth. It can also beadministered orally in the form of a solution or syrup, or it can beinjected parenterally. For parenteral administration it can be used inthe form of a sterile solution, preferably of pH 7.2-7.6 containing apharmaceutically acceptable buffer. Oral and parenteral administrationare the preferred routes for treating neuropathy and nephropathy in adiabetic mammal.

The dosage of the present therapeutic agent can vary with the form ofadministration. Furthermore, it can vary with the particular host undertreatment. Generally, treatment is initiated with small dosagessubstantially less than the optimal dose of the compound. Thereafter,the dosage is increased by small increments until the optimal effectunder the circumstances is reached. In general,5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid is most desirably administered at a concentration level that willgenerally afford effective results without causing any harmful ordeleterious side effects. For topical administration, a 0.05 to 0.2%solution can be administered dropwise to the eye. The frequency ofinstallation varies with the subject under treatment from a drop everytwo or three days to once daily. For oral or parenteral administration apreferred level of dosage ranges from about 0.1 mg to about 200 mg perkilogram of body weight per day, although aforementioned variations willoccur. However, a dosage level that is in the range of from about 3.0 mgto about 30 mg per kilogram of body weight per day is most satisfactory.

Unit dosage forms such as capsules, tablets, pills and the like cancontain from about 5 mg to about 50 mg of5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid dependent on the type of unit dosage, preferably with a significantquantity of a pharmaceutical carrier. Thus, for oral administration,capsules can contain from between about 5 mg to about 50 mg of5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid with or without a pharmaceutical diluent. Tablets, eithereffervescent or noneffervescent, can contain between about 5 to 50 mg of5-fluoro-2-methyl-1-[[4-(methylthio]phenyl]methylene]-1H-indene-3-aceticacid together with conventional pharmaceutical carriers. Thus, tabletswhich can be coated and either effervescent or noneffervescent can beprepared according to the known art. Inert diluents or carriers, forexample, magnesium carbonate or lactose, can be used together withconventional disintegrating agents, for example, maize starch andalginic acid and lubricating agents for example, magnesium stearate.

Syrups or elixirs suitable for oral administration can be prepared fromwater soluble salts, for example, the sodium salt of5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid and can advantageously contain glycerol and ethyl alcohol assolvents or preservatives.

5-Fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid, or a therapeutically acceptable salt thereof, also can be used incombination with insulin or oral hypoglycemic agents to producebeneficial effect in the treatment of diabetes mellitus. In thisinstance, commercially available insulin preparations or oralhypolycemic agents, exemplified by acetohexamide, chlorpropamide,tolazamide, tolbutamide and phenformin, are suitable.5-Fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid, or a therapeutically acceptable salt thereof, can be administeredsequentially or simultaneously with insulin or the oral hypoglycemicagent. Suitable methods of administration, compositions and doses of theinsulin preparation or oral hypoglycemic agent are described in medicaltextbooks; for instance, "Physicians' Desk Reference", 34 ed., MedicalEconomics Co., Oradell, N.J., U.S.A., 1980, "AMA Drug Evaluations", 3rded., PSG Publishing Co., Inc., Littleton, Mass., U.S.A., 1977, pp.582-598, and "The Pharmacological Basis of Therapeutics", L. S. Goodmanand A. Gilman, Eds., 5th ed., Macmillan Publishing Co., Inc., New York,N.Y., U.S.A., 1975, pp. 1507-1533. When used in combination,5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid, or its therapeutically acceptable salt, is administered asdescribed previously.5-Fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid, or its therapeutically acceptable salt, can be administered withthe oral hypoglycemic agent in the form of a pharmaceutical compositioncomprising effective amounts of each agent.

The aldose reductase inhibiting effects of5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid or its pharmaceutically acceptable salts with an organic orinorganic base can be demonstrated by employing an in vitro testingprocedure similar to that described by S. Hayman and J. H. Kinoshita, J.Biol. Chem., 240, 877 (1965). In the present case the procedure ofHayman and Kinoshita is modified in that the final chromatography stepis omitted in the preparation of the enzyme from bovine lens.

When evaluated in the above in vitro test,5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid exhibited a 50 percent inhibition at a concentration of 1×10⁻⁶ M.

The aldose reductase inhibiting property of5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid and its utilization in diminishing and alleviating diabeticcomplications also are demonstrable in experiments using galactosaemicrats, see D. Dvornik et al., Science, 182, 1146 (1973). Such experimentsare exemplified hereinbelow after the listing of the following generalcomments pertaining to these experiments:

(a) Four or more groups of six male rats, 50-70 g, Sprague-Dawleystrain, were used. The first group, the control group, was fed a mixtureof laboratory chow (rodent laboratory chow, Purina) and glucose at 20%(w/w %) concentration. The untreated galactosaemic group was fed asimilar diet in which galactose is substituted for glucose. The othergroups were fed diets containing various amounts of5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]-methylene]-1H-indene-3-aceticacid in the galactose containing diet. The concentration of galactose inthe diet of the treated groups was the same as that for the untreatedgalactosaemic group.

(b) After four days, the animals were killed by decapitation. Theeyeballs were removed and punctured with a razor blade; the freed lenseswere rolled gently on filter paper and weighed. The sciatic nerves weredissected as completely as possible and weighed. Both tissues werefrozen and kept up to two weeks before being analyzed for dulcitol.

(c) The tissues were homoginized in 5% (w/v) trichloroacetic acid andthe polyol determination on the extracts was performed by a modificationof the procedure of M. Kraml and L. Cosyns, Clin. Biochem., 2, 373(1969). Only two minor reagent changes were made: (a) The rinsingmixture was an aqueous 5% (w/v) trichloroacetic acid solution and (b)the stock solution was prepared by dissolving 25 mg of dulcitol in 100ml of an aqueous trichloroacetic acid solution. [N.B.: For eachexperiment the average value found in the tissue from rats fed theglucose diet was substracted from the individual values found in thecorresponding rat tissue to obtain the amount of polyol accumulated].

The following results show that5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid diminishes and alleviates the accumulation of galactitol in thelenses and sciatic nerves of rats fed galactose as compared to anuntreated animal: at a dose of 88 mg/kg/day exhibited a 20±4 percentdecrease in galactitol accumulation in the lens and a 31±12 percentdecrease in galactitol accumulation in the sciatic nerve.

We claim:
 1. A method of preventing or relieving a diabetic complicationin a diabetic mammal which comprises administering to said mammal aneffective alleviating or prophylactic amount of5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid, or a therapeutically acceptable salt thereof with an organic orinorganic base.
 2. The method of claim 1 wherein said diabeticcomplication is selected from cataracts, neuropathy, nephropathy andretinopathy.
 3. A method of preventing or relieving diabetes mellitusassociated complications consisting of cataracts and retinopathy in adiabetic mammal which comprises topically administering to said mammalan effective alleviating or prophylatic amount of a sterile aqueoussolution of5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid, or a therapeutically acceptable salt thereof with an organic orinorganic base.
 4. A method of preventing or relieving diabetes mellitusassociated complications consisting of neuropathy and nephropathy in adiabetic mammal which comprises orally or parenterally administering tosaid mammal an effective alleviating or prophylactic amount of5-fluoro-2-methyl-1-[[4-(methylthio)phenyl]methylene]-1H-indene-3-aceticacid, or a therapeutically acceptable salt thereof with an organic orinorganic base.